Just make sure you have correct S3 version (i747 for Rogers version - same as AT&T). Also - make sure you install RECOVERY on it (and test that you can boot into it). After that you should be good to go (for most cases).

I bought an S3 off kijiji and the seller lied to me about the phone never being rooted. I'm not a power user and I didn't want to buy a previously rooted phone but now I'm stuck with it. Now for damage control. I tried to do a software update add I'm version 4.1.1 and I thought I could update to a newer version but the phone says "device modified" and unable to update. Is this forever? I did a hard reboot, restarted etc. All the things to get it to say normal under device status but to no avail. I know some people were getting that modified status despite never having rooted their phones so I'm going this is some kind of glitch. It's an unlocked Rogers/Fido phone. Please help...

I bought an S3 off kijiji and the seller lied to me about the phone never being rooted. I'm not a power user and I didn't want to buy a previously rooted phone but now I'm stuck with it. Now for damage control. I tried to do a software update add I'm version 4.1.1 and I thought I could update to a newer version but the phone says "device modified" and unable to update. Is this forever? I did a hard reboot, restarted etc. All the things to get it to say normal under device status but to no avail. I know some people were getting that modified status despite never having rooted their phones so I'm going this is some kind of glitch. It's an unlocked Rogers/Fido phone. Please help...

Is the phone running a stock carrier OS? If not, what rom is it running?

Personally, I prefer a re-rooted phone as it allows you to load custom roms, use Titanium Backup, etc.